Good first DSO Joel. Yes DSO AP is quite a beast, but very addictive. As your exposures get longer, you might want to take more darks and add some flats and dark flats. Some people take biases, but I just take dark flats instead. Good luck and look forward to seeing some more.

Thanks for the kind words, everyone! I'm glad I dabbled in planetary/lunar imaging first; I've got a decent hang of polar alignment and processing already, which eliminates some of the frustration.

I'm going to need to read up on taking flats and bias frames. As far as the number of dark frames to take, is there a ratio to shoot for, say, one dark frame for every two light frames or something like that?

Not a ratio. Even if you take only one light frame you would want to take a large number of dark frames. Commonly you will see numbers of at least 12-20. Personally, I shoot for at least 20. The benefit goes up as the square root of the number shot. So if you double the number you take, the noise goes down by about 1.4. So 20 will have about 1.29 times less noise than 12.

If you do darks wrong (wrong temperature, incorrect time, etc.) you could actually introduce more noise than you got rid of.

For the really bright emission nebula like M42 you will get pleasing shots even with an unmodded camera. You won't capture the dimmest parts but you'll still have something that looks good. For dimmer ones, you will still be able to capture something but it won't be very good. Here is an example of the Helix I shot with an unmodded Canon 50d.

I've been trying to get this with a video cam that I use to get most of my shots. I can't get it near that crisp and I've ben tring lots of diffret things. This gives me a model to shoot for and to referance! Well done!